Method for detecting a blocking of a rotor of a motor driving an actuator member

ABSTRACT

A method of detecting blocking of a rotor of a motor driving an actuator member with movement in translation between a first abutment and a second abutment, the method comprising the steps of, during an angular movement of the rotor, estimating at least a position (X) of the actuator member relative to the two abutments, a travel direction of the actuator member relative to the two abutments, and also a travel speed (V) of the actuator member; and on the basis at least of the estimated position of the actuator member, of the estimated travel direction of the actuator member, and of the estimated travel speed of the actuator member, detecting blocking of the rotor.

The invention relates to a method of detecting the blocking of a rotorof a motor driving an actuator member.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

In an aircraft, various movable elements such as control surfaces orindeed the cowl of a thrust reverser are associated with actuatormembers in order to be moved between a neutral position and an activeposition. For this purpose, the actuator members are driven by a motorto move in translation between two abutments. By way of example, for aflap, a first abutment is associated with the neutral position of themovable element, and a second abutment is associated with the activeposition of the movable element. Under such circumstances, when themotor is powered, it drives the actuator members that in turn move theassociated movable members.

Nevertheless, the rotor of the motor might be subjected to mechanicalblocking. In spite of the blocking, the electrical power that isdelivered to the motor remains identical, thereby leading to overheatingof the motor, and in particular of its power electronics. This can leadto degradation of the motor.

One solution would be to design the power electronics of the motor insuch a manner as to enable it to withstand overheating as a result ofthe rotor being blocked. However, that would lead to an increase in theweight and in the size of the power electronics, which is not desirablein the field of aviation.

Another solution would be to detect overheating by means of a thermalrelay. Nevertheless, such a relay presents a response time that isrelatively long and therefore does not enable overheating to be detectedquickly. The power electronics could thus still be damaged in spite ofthe presence of the relay. Furthermore, the relay does not make itpossible to distinguish between a problem of overheating due to agenuine blockage of the rotor, and a problem of overheating due to someother reason. Any action taken after the relay has detected overheatingmight therefore not be appropriate.

OBJECT OF THE INVENTION

An object of the invention is to propose a method of detecting theblocking of a motor that drives an actuator member, which method makesit possible to detect blocking of the rotor of said motor moreeffectively.

BRIEF SUMMARY OF THE INVENTION

In order to achieve this object, the invention provides a method ofdetecting blocking of a rotor of a motor driving an actuator member tomove in translation between first and second abutments that arerespectively representative of first and second angular positions and asecond angular position of the rotor, the method comprising the stepsof:

-   -   during angular movement of the rotor, estimating at least a        position of the actuator member relative to the two abutments, a        travel direction of the actuator member relative to the two        abutments, and also a travel speed of the actuator member;    -   on the basis at least of the estimated position of the actuator        member, of the estimated travel direction of the actuator        member, and of the estimated travel speed of the actuator        member, detecting:        -   blocking of the rotor due to the actuator member reaching            the first abutment; or        -   blocking of the rotor due to the actuator member reaching            the second abutment; or        -   blocking of the rotor due to seizing during travel of the            actuator member towards the first abutment; or        -   blocking of the rotor due to seizing during travel of the            actuator member towards the second abutment.

As a result of continuously observing parameters that are easilymeasured or quantified, the method of the invention makes it possiblenot only to detect any blocking of the rotor quickly, but also toestimate whether the blocking is due to seizing or to coming intoabutment. Consequently, it is possible to respond quickly with differentactions depending on the type of blocking that has been detected.

The method of the invention thus makes it possible to detect blocking ofthe rotor of the motor in a manner that is effective.

Furthermore, the method of the invention may be performed by means thatrequire maintenance costs that are low compared with a thermal relay orwith oversized power electronics for the motor.

Advantageously, the method of the invention makes it possible to detectblocking of a motor driving an actuator member associated with one ormore movable elements that are subjected to forces that vary over timeand position (as a function of the position of the movable element). Forexample, when the movable element is a movable outside portion of anaircraft (thrust reversal cowl, control surface, aileron, . . . ), saidmovable element is subjected to aerodynamic loads that vary in time andin position.

For the present application, when mention is made of data characteristicof the actuator member, such as for example the position of the actuatormember, that can apply equally well to data that is actually associatedwith the actuator member, such as the actual position of the actuatormember, or to data that is representative of the actuator member, butthat is actually associated with the rotor, such as the actual angularposition of the rotor, which is in fact representative of the actualposition of the actuator member as a result of the connection betweenthe actuator member and the rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood in the light of the followingdescription of a particular, non-limiting implementation of theinvention. Reference is made to the accompanying figures, in which:

FIG. 1 is a diagrammatic view of a control surface, of an actuatormember, and of a motor associated with said control surface, togetherwith control means for the motor enabling the method of the invention tobe performed;

FIG. 2 is a diagrammatic view of a detector module of the control meansshown in FIG. 1;

FIG. 3 is a flow chart associated with the detector module shown in FIG.2 and showing a first detection of a rotor of the motor blocking, due tothe actuator member reaching the first abutment;

FIG. 4 is a flow chart analogous to FIG. 3 showing a second detection ofthe rotor of the motor blocking, due to the actuator member reaching thesecond abutment;

FIG. 5 is a flow chart analogous to FIG. 3 showing a third detection ofthe rotor of the motor blocking, due to seizing while the actuatormember is moving towards the first abutment; and

FIG. 6 is a flow chart analogous to FIG. 3 showing a fourth detection ofthe rotor of the motor blocking, due to seizing while the actuatormember is moving towards the second abutment.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 and 2, the detection method of the inventionis used in this example to detect blocking of a rotor of a motor 1driving an actuator member 2 for actuating a control surface 3 of anaircraft. Naturally, this application is not limiting, and the method ofthe invention may be implemented to detect blocking of a rotor of amotor driving an actuator member associated with some other movableelement, such as for example the cowl of a thrust reverser of anaircraft.

In this example, the motor 1 is a permanent magnet synchronous machine.

In known manner, the actuator member 2 is for moving the control surface3 between two extreme positions. For this purpose, the actuator member 2is associated with the motor 1 so as to be driven by said motor 1 tomove in translation between a first abutment and a second abutment, suchthat:

-   -   when the actuator member 2 is at the first abutment, the control        surface 3 is in its first extreme position, with the respective        positions of the actuator member 2 and of the control surface 3        then being drawn in continuous lines; and    -   when the actuator member 2 is at the second abutment, the        control surface 3 is in its second extreme position, with the        respective positions of the actuator member 2 and of the control        surface 3 then being drawn in dashed lines.

The first abutment and the second abutment are representativerespectively of a first angular position and of a second angularposition of the rotor of the motor 1.

As a result, when the motor 1 is powered, it drives the actuator member2, which in turn moves the control surface 3.

Furthermore, the motor 1 is associated with control means 4 forcontrolling the motor 1. In order to detect blocking of the rotor,during angular movement of the rotor, the control means 4 include adetector module 5 for detecting blocking of the rotor.

For this purpose, whenever the rotor is moving angularly, the detectormodule 5 receives the following data from the control means 4: theposition X of the actuator member 2 relative to the two abutments; thetravel direction of the actuator member 2 relative to said abutments;and the travel speed V of the actuator member 2. By way of example, theposition X of the actuator member 2 and the travel speed V of theactuator member 2 are measured by sensors connected to the control means4. In a variant, the position X of the actuator member 2 and the travelspeed V of the actuator member 2 are deduced from corresponding dataassociated with the motor, which data may be supplied by a resolver ofthe control means 4, for example.

In this example, the information about the travel direction of theactuator member 2 is transmitted to the detector module 5 via an ORDERvariable that takes the value GO when the actuator member 2 is movingtowards the second abutment, and that takes the value BACK when theactuator member 2 is moving towards the first abutment. The value of thevariable ORDER is modified by the control means 4 depending on thesetpoints applied to the motor 1.

In particular manner, throughout the angular movement of the rotor, thedetector module 5 also receives the travel speed setpoint data V* fromthe actuator member, which is transmitted thereto by the control means4.

Furthermore, in this example, throughout the angular movement of therotor, the detector module 5 receives the setpoint data C* for themechanical torque to be delivered to the actuator member 2, which datais transmitted to the detector module by the control means 4.

Furthermore, the positions of the first abutment But_1 and of the secondabutment But_2 are stored in the detector module 5. In this example, theposition of the first abutment But_1 corresponds to zero and theposition of the second abutment But_2 corresponds to a positive valueother than zero.

Furthermore, in this example, a minimum travel speed threshold V_min forthe actuator member 2 is stored in the detector module 5. Specifically,if the actuator member 2 travels too slowly, that can lead tooverheating of the motor 1, which might damage it. Said minimum travelspeed threshold V_min is thus predetermined so as to avoid an excessivetemperature rise of the motor 1.

In the same manner, in this example, a maximum mechanical torquethreshold C_max for delivery to the actuator member 2 is stored in thedetector module 5. Furthermore, a minimum mechanical torque thresholdC_min for delivery to the actuator member 2 is also stored in thedetector module 5. Specifically, it should be recalled that the actuatormember 2 is movable reversibly between two abutments. The mechanicaltorque setpoint is thus positive when the actuator member 2 is movingtowards the second abutment, and must thus be less than C_max, and it isnegative when the actuator member 2 is traveling towards the firstabutment, and must thus be greater than C_min (which is a negativevalue).

These mechanical torque thresholds are predetermined so as to avoidmechanical damage to the motor 1 or to the actuator member 2, e.g. as aresult of too great a demand on said motor 1 or on the actuator member2.

In addition, a position uncertainty dX is stored in the detector module5. This position uncertainty dX defines a position error of the actuatormember 2 relative to the position X, and in particular it ispredetermined so as to take into consideration inaccuracy concerning themeasurement of the position dX by the sensor.

This data concerning position X, travel direction ORDER, travel speed V,travel speed setpoint V*, mechanical torque setpoint C*, position of thefirst abutment But_1, position of the second abutment But_2, and alsothe values of the minimum travel speed threshold V_min, the maximummechanical torque threshold C_max, the minimum mechanical torquethreshold C_min, and the position uncertainty dX serves to enable thedetector module 5 to detect blocking of the rotor and also to determinewhether the blocking is due to the actuator member 2 coming intoabutment or due to seizing of the motor 1 or of the actuator member 2.More precisely, the detector module 5 is configured to determine whetherthe blocking is due to the actuator member 2 reaching the firstabutment, or is due to the actuator member 2 reaching the secondabutment, or is due to seizing during travel of the actuator member 2towards the first abutment, or is due to seizing during travel of theactuator member 2 towards the second abutment.

In a particular implementation, the detector module 5 includes indexingmeans 6 generating a STALL variable for use by the control means 4 bycausing said STALL variable to take a particular value depending on thetype of blocking that has been detected, as described below.

During angular movement of the rotor, so long as blocking has not beendetected, the indexing means 6 maintain the STALL variable at 0.

With reference to FIG. 3, the detector module 5 detects blocking of therotor due to the actuator member 2 reaching the second abutment:

-   -   if the position of the actuator member 2 is significantly        greater than or equal to the position of the second abutment        But_2, i.e. in this example if the position X of the actuator        member 2 is greater than or equal to the position of the second        abutment But_2 minus the position uncertainty dX; and    -   if the absolute value of the difference between the travel speed        setpoint V* and the travel speed V is greater than or equal to        zero; and    -   if the absolute value of the travel speed V is less than or        equal to the minimum travel speed threshold V_min; and    -   if the travel order to the actuator member towards the second        abutment is active, i.e. if the ORDER variable is equal to GO.

Under such circumstances, the indexing means 6 increment the value ofthe STALL variable so that the STALL variable becomes 1.

So long as the order to move towards the second abutment is active, i.e.so long as the ORDER variable is equal to GO, the STALL variable remainsat 1.

When the order to move towards the second abutment is no longer active,i.e. if the ORDER variable is not equal to GO, then the indexing means 6modify the value of the STALL variable so that it once more becomes 0.The detector module 5 is thus ready to detect new blocking of the rotor.

With reference to FIG. 4, the detector module 5 detects blocking of therotor due to the actuator member 2 reaching the first abutment:

-   -   if the position of the actuator member 2 is substantially less        than or equal to the position of the first abutment But_1, i.e.        in this example, if the position of the actuator member 2 is        less than or equal to the position of the first abutment But_1        plus the position uncertainty dX; and    -   if the absolute value of the difference between the travel speed        setpoint V* and the travel speed V is greater than or equal to        zero; and    -   if the absolute value of the travel speed V is less than or        equal to the minimum travel speed threshold V_min; and    -   if an order to move the actuator member 2 towards the first        abutment is active, i.e. if the ORDER variable is equal to BACK.

Under such circumstances, the indexing means 6 increment the value ofthe STALL variable so that the STALL variable becomes 2.

So long as the order to move towards the first abutment is active, i.e.so long as the ORDER variable is equal to BACK, the STALL variableremains at 2.

When the order to move towards the first abutment is no longer active,i.e. when the ORDER variable is no longer equal to BACK, the indexingmeans 6 modify the value of the STALL variable so that it is once moreequal to 0. The detector module 5 is thus ready to detect new blockingof the rotor.

With reference to FIG. 5, the detector module 5 detects blocking of themotor due to seizing while the actuator member 2 is moving towards thesecond abutment:

-   -   if the absolute value of the difference between the maximum        torque threshold C_max and the torque setpoint C* is        substantially zero over at least a given time interval, e.g. in        this example over a time interval of at least 3 milliseconds        (ms);    -   if the position X is substantially less than the position of the        second abutment But_2 and substantially greater than the        position of the first abutment But_1, i.e. in this example if        the position X is less than the position of the second abutment        But_2 minus the position uncertainty dX and greater than the        position of the first abutment But_1 plus the position        uncertainty dX; and    -   if the absolute value of the travel speed V is less than the        minimum travel speed threshold V_min; and    -   if an order to move the actuator member 2 towards the second        abutment is active, i.e. if the ORDER variable is equal to GO.

Under such circumstances, the indexing means 6 increment the value ofthe STALL variable so that the STALL variable becomes 3.

So long as the order to move towards the second abutment is active, i.e.the ORDER variable is equal to GO, and so long as the absolute value ofthe travel speed V remains less than the minimum travel speed thresholdV_min, the STALL variable remains at 3.

When the order to move towards the second abutment is no longer active,i.e. when the ORDER variable is no longer equal to GO, the indexingmeans 6 modify the value of the STALL variable so that it is once moreequal to 0. Furthermore, when the absolute value of the travel speed Vbecomes greater than the minimum travel speed threshold V_min, theindexing means 6 modify the value of the STALL variable so that it isonce more equal to 0.

In both situations, the detector module 5 is ready to detect newblocking of the rotor.

Finally, with reference to FIG. 6, the detector module 5 detectsblocking of the rotor due to seizing during movement of the actuatormember 2 towards the first abutment:

-   -   if the absolute value of the difference between the minimum        torque threshold C_min and the torque setpoint C* is        substantially zero for at least a given time interval, which in        this example is equal to 3 ms; and    -   if the position X is substantially less than the position of the        second abutment But_2 and substantially greater than the        position of the first abutment But_1, i.e., in this example, if        the position X is less than the position of the second abutment        But_2 minus the position uncertainty dX and greater than the        position of the first abutment But_1 plus the position        uncertainty; and    -   if the absolute value of the travel speed V is less than the        minimum travel speed threshold V_min; and    -   if an order to move the actuator member towards the first        abutment is active, i.e. if the ORDER variable is equal to BACK.

Under such circumstances, the indexing means 6 increment the value ofthe STALL variable so that the STALL variable becomes 4.

So long as the order to move towards the first abutment is active, i.e.the ORDER variable is equal to BACK, and so long as the absolute valueof the travel speed V remains less than the minimum travel speedthreshold V_min, the STALL variable remains at 4.

When the order to move towards the first abutment is no longer active,i.e. when the ORDER variable is no longer equal to BACK, the indexingmeans 6 modify the value of the STALL variable so that it is once moreequal to zero. Furthermore, when the absolute value of the travel speedV is greater than the minimum travel speed threshold V_min, the indexingmeans 6 modify the value of the STALL variable so that it is once moreequal to 0.

In both situations, the detector module 5 is once more ready to detectnew blocking of the rotor.

As a result, on the basis of simple data items that are easilydetermined or measured, the detector module 5 can determine quickly andeffectively that blocking has occurred and can even determine the causeof the blocking.

Advantageously, the indexing means 6 make it possible to indicateclearly and quickly to the control means 4 the type of the blocking thathas been detected. It is then possible for the control means 4 to actappropriately depending on the value taken by the STALL variable.

In a particular implementation, the control means 4 are thus arranged toact, whenever it has been detected that the rotor is blocked as a resultof the actuator member 2 reaching the first abutment or the secondabutment, i.e. whenever the STALL variable generated by the indexingmeans is equal to 1 or 2.

Preferably, when the STALL variable is equal to 1 or 2, the controlmeans 4 control the motor 1 so as to lead to fictitious braking of theactuator member 2.

In particular manner, in this example, the control means 4 reduce thevalue of the maximum torque threshold C_max when the STALL variable isequal to 1. The maximum torque threshold C_max in this example isreduced so that the motor 1 can nevertheless maintain the controlsurface 3 in its extreme position by using the actuator member 2 tooppose aerodynamic forces, in particular.

Because of this reduction in the maximum torque C_max that may betransmitted to the actuator member 2, the motor 1 is powered with lesspower. As a result, even though the actuator member 2 remains inabutment over a relatively long length of time, there is no excessiveoverheating of the motor 1.

Likewise, in this example, the control means 4 increase the value of theminimum torque threshold C_min (a negative value) when the STALLvariable is equal to 2. In this example, the minimum torque thresholdC_min is increased so that the motor 1 manages nevertheless to keep thecontrol surface 3 in its extreme position by using the actuator member 2to oppose aerodynamic forces, in particular. In a particularimplementation, the control means 4 are also arranged to act when it isdetected that the rotor is blocked as a result of seizing, i.e. when theSTALL variable generated by the indexing means 6 is equal to 3 or 4.

In particular manner, when the STALL variable is equal to 3 or 4, thecontrol means 4 control the motor 1 by requesting the rotor to performsuccessive small angular movements through small amplitudes in onedirection of rotation and then in the other direction of rotation,corresponding to ordering successive go-and-return movements of theactuator member 2 through small amplitudes, in order to release themotor 1 and/or the actuator member 2.

Naturally, the invention is not limited to the implementation described,and variant implementations may be applied thereto without going beyondthe ambit of the invention.

In particular, although in this example use is made directly ofmeasurements of the travel and the position of the actuator member inorder to detect blocking, it is possible to detect blocking by havingrecourse to models that are representative of the movement of theactuator member. For example, the model may serve to model the angularmovement of the rotor between its first angular position and its secondangular position by a movement in translation of a body having the sameinertia as the rotor between two abutments, each abutment beingrepresentative of a respective abutment of the actuator member. Modelscould also be used to determine the thresholds used by the method of theinvention such as the minimum speed threshold. Although use is made inthis example of data associated with the actuator member, the method ofthe invention could be implemented using data associated with the rotorand representative of data associated with the actuator member. Oncemore, in the present application, when reference is made to data that ischaracteristic of the actuator member, such as the mechanical torquesetpoint for transmitting to the actuator member, that could equallywell be data that is associated with the actuator member, namely a realsetpoint for the mechanical torque to be transmitted to the actuatormember, or data that is representative of the actuator member but thatis associated with the rotor, such as a setpoint for the electromagnetictorque to be delivered to the rotor and that is representative of thesetpoint for the mechanical torque to be transmitted to the actuatormember. Thus, data associated with the motor and representative of dataassociated with the actuator member may be supplied by a resolver of themotor.

Although in this example the motor is controlled requesting the rotor toperform successive small amplitude angular movements in one direction ofrotation and then in the other direction of rotation in order to unblockthe rotor in the event of seizing, it is possible in a variant, or inaddition, to control the motor in some other way in an attempt tounblock the rotor in the event of seizing. For example, the maximummechanical torque threshold for transmission to the actuator membercould be increased during a predetermined time interval, e.g. 3 ms (orconversely the minimum mechanical torque threshold to be transmitted tothe actuator member, which threshold is negative, could be decreasedduring a predetermined time interval, e.g. 3 ms). It is also possible toswitch off the electrical power supply to the motor in order to avoiddamaging the motor and/or the actuator member as a result of seizing.For example, if neither causing the rotor to perform successive smallmovements in rotation in both directions of rotation, nor temporarilyincreasing the absolute maximum torque enable the rotor to be unblocked,then the electrical power supply to the motor may be cut off.

Although in the present example there is only one minimum travel speedthreshold, there could be two minimum travel speed thresholds, andparticularly, but not exclusively, in the event of maximum and minimumtorque thresholds being modified when the actuator member is in abutmentor close to the abutments: there could be a first minimum travel speedthreshold for when the actuator member is traveling towards one or theother of its abutments, and a second minimum travel speed threshold forwhen the actuator member is already in abutment or in the proximity ofits abutment. The first threshold should then be used for detectingblocking of the rotor due to seizing, and the second threshold fordetecting blocking of the rotor due to the actuator member coming intoabutment.

Although in this example the values for the torque threshold aremodified only when the actuator member is in abutment, said values couldbe modified all along the travel of the actuator member in order tobrake said travel progressively on approaching the abutment.

1. A method of detecting blocking of a rotor of a motor driving anactuator member to move in translation between first and secondabutments that are respectively representative of first and secondangular positions of the rotor, the method comprising the steps of:during angular movement of the rotor, estimating at least a position ofthe actuator member relative to the two abutments, a travel direction ofthe actuator member relative to the two abutments, and also a travelspeed of the actuator member; on the basis at least of the estimatedposition of the actuator member, of the estimated travel direction ofthe actuator member, and of the estimated travel speed of the actuatormember, detecting: blocking of the rotor due to the actuator memberreaching the first abutment; or blocking of the rotor due to theactuator member reaching the second abutment; or blocking of the rotordue to seizing during travel of the actuator member towards the firstabutment; or blocking of the rotor due to seizing during travel of theactuator member towards the second abutment.
 2. The method according toclaim 1, wherein blocking of the rotor due to the actuator memberreaching the second abutment is detected: if the position of theactuator member is substantially greater than or equal to the positionof the second abutment; and if an absolute value of the differencebetween a travel speed setpoint for the actuator member and the travelspeed of the actuator member is greater than or equal to zero; and ifthe absolute value of the travel speed of the actuator member is lessthan or equal to a predetermined minimum travel speed threshold; and ifan order for movement of the actuator member towards the second abutmentis active, which order is representative of the travel direction of theactuator member.
 3. The method according to claim 1, wherein blocking ofthe rotor due to the actuator member reaching the first abutment isdetected: if the position of the actuator member is substantially lessthan or equal to the position of the first abutment; and if an absolutevalue of the difference between a travel speed setpoint for the actuatormember and the travel speed of the actuator member is greater than orequal to zero; and if the absolute value of the travel speed of theactuator member is less than or equal to a predetermined minimum travelspeed threshold; and if an order for movement of the actuator membertowards the first abutment is active, which order is representative ofthe travel direction of the actuator member.
 4. The method according toclaim 1, wherein blocking of the rotor due to, seizing during travel ofthe actuator member towards the second abutment is detected: if theposition of the actuator member is substantially less than the positionof the second abutment and substantially greater than the position ofthe first abutment; and if an absolute value of the travel speed of theactuator member is less than a predetermined minimum travel speedthreshold; and if an absolute value of the difference between apredetermined maximum torque threshold and a torque setpoint fortransmitting to the actuator member is substantially zero for at least apredetermined time interval; and if an order to move the actuator membertowards the second abutment is active, which order is representative ofa travel direction of the actuator member.
 5. The method according toclaim 1, wherein blocking of the rotor due to seizing during travel ofthe actuator member towards the first abutment is detected: if theposition of the actuator member is substantially less than the positionof the second abutment and substantially greater than the position ofthe first abutment; and if an absolute value of the travel speed of theactuator member is less than a predetermined minimum travel speedthreshold; and if an absolute value of the difference between apredetermined minimum torque threshold and a torque setpoint fortransmitting to the actuator member is substantially zero for at least apredetermined time interval, the predetermined minimum torque thresholdbeing a negative value; and if an order to move the actuator membertowards the first abutment is active, which order is representative of atravel direction of the actuator member.
 6. The method according toclaim 1, further including a step of releasing the rotor when it isdetected that blocking is due to seizing.
 7. The method according toclaim 6, wherein during the step of releasing the rotor, the rotor iscontrolled to perform angular movements of small amplitude successivelyin one direction of rotation and then in the other direction of rotationof the rotor.
 8. The method according to claim 6, wherein during thestep of releasing the rotor, a maximum mechanical torque threshold fortransmitting to the actuator member is increased during a predeterminedtime interval.
 9. The method according to claim 6, wherein during thestep of releasing the rotor, the power supply to the motor is cut off.10. The method according to claim 1, further including a step offictitious braking of the actuator member when blocking is detected dueto the actuator member coming into abutment.
 11. The method according toclaim 10, wherein a maximum mechanical torque threshold, of positivevalue, for transmitting to the actuator member is reduced when it isdetected that blocking is due to the actuator member coming intoabutment.
 12. The method according to claim 10, wherein a minimummechanical torque threshold, of negative value, for transmitting to theactuator member is increased when it is detected that blocking is due tothe actuator member coming into abutment.